On 02/21/2012 07:10 PM, Tomoya MORINAGA wrote:> 2012年2月22日10:59 Darren Hart <dvhart@linux.intel.com>:>> This series does some minor clean-up to the pch_uart driver, adds support>> for the Fish River Island II UART clock, and introduces a user_uartclk>> parameter to aid in developing for early and changing hardware.>>>> Note that this series is my proposed alternative solution to that provided>> by Tomoya MORNIAGA and Feng Tang which drops the board quirks and opts to>> assume a 192 MHz clock on all boards. The problem with this approach is>> that the CLKCFG register may have been set to something other than the>> 192MHz configuration by the firmware. If so, then the pch_uart will send>> garbage between the time the boot console is disabled and the pch_phub>> sets the CLKCFG register again. In my case, the pch_phub PCI probe occurs>> after the pch_uart_console_setup. Even if it happened before, the output>> up until the PCI probing would be garbage.>>>> In order to support an early serial console, we cannot rely on the pch_phub>> probe function to setup the CFGCLK register. This series relies on the board>> quirks and doesn't force the setting of the CLKREG in the pch_phub code.>> Instead, it aligns with what is the default configuration (defined by firmware)>> for a given board. The user_uartclk provides a mechanism to force a specific>> uartclk if necessary.> > I think UART console function(including "early serial console") is> used for debug use.> > So, if people who want to see the boot log correctly before pch_phub installed,> the people have only to do configure uart_clock by themselves.> > So, I think default uart_clock 192MHz setting is better than Darren's opinion.> > Let me know your opinion.

This patch series allows for a functional early serial console as wellas using the UART after boot. It leaves the CM-iTC board alone. So thisseems to enable all use cases, while forcing 192MHz breaks the FRI2early serial console. I don't see an advantage to that approach otherthan the obviously simpler code (which is nice, but should not trumpfunctionality).